Dissecting spinal cord regeneration.

The inability to recover functions lost after severe spinal cord injury has been recognized for millennia and was first attributed to a failure of spinal cord neural regeneration over 100 years ago. The last forty years have seen intense research into achieving such regeneration, but in spite of conceptual advances and many reports announcing successful interventions, progress has been slow and often controversial. Here, I examine consequential advances and setbacks, and critically consider assumptions underlying certain approaches. I argue that expanding mechanistic knowledge about multiple forms of neural regeneration, why they fail and how they can restore function will resolve conceptual contentions and push the field forward.

Increased Synthesis of Chondroitin Sulfate Proteoglycan Promotes Adult Hippocampal Neurogenesis in Response to Enriched Environment.

Chondroitin sulfate proteoglycan (CSPG) is a candidate regulator of embryonic neurogenesis. The aim of this study was to specify the functional significance of CSPG in adult hippocampal neurogenesis using male mice. Here, we showed that neural stem cells and neuronal progenitors in the dentate gyrus were covered in part by CSPG. Pharmacological depletion of CSPG in the dentate gyrus reduced the densities of neuronal progenitors and newborn granule cells. 3D reconstruction of newborn granule cells showed that their maturation was inhibited by CSPG digestion. The novel object recognition test revealed that CSPG digestion caused cognitive memory impairment. Western blot analysis showed that expression of ß-catenin in the dentate gyrus was decreased by CSPG digestion. The amount of CSPG in the dentate gyrus was increased by enriched environment (EE) and was decreased by forced swim stress. In addition, EE accelerated the recovery of CSPG expression in the dentate gyrus from the pharmacological depletion and promoted the restoration of granule cell production. Conversely, the densities of newborn granule cells were also decreased in mice that lacked chondroitin sulfate N-acetylgalactosaminyltransferase 1 (CSGalNAcT1), a key enzyme for CSPG synthesis (T1KO mice). The capacity of EE to promote granule cell production and improve cognitive memory was impaired in T1KO mice. These findings indicate that CSPG is involved in the regulation of adult hippocampal neurogenesis and suggest that increased synthesis of CSPG by CSGalNacT1 may mediate promotion of granule cell production and improvement of cognitive memory in response to EE.SIGNIFICANCE STATEMENT Chondroitin sulfate proteoglycan (CSPG) is a candidate regulator of embryonic neurogenesis. Here, we specified the role of CSPG in adult neurogenesis in the mouse hippocampus. Digestion of CSPG in the dentate gyrus impaired granule cell production and cognitive memory. Enriched environment (EE) promoted the recovery of CSPG expression and granule cell production from the CSPG digestion. Additionally, adult neurogenesis was impaired in mice that lacked a key enzyme for CSPG synthesis (T1KO mice). The capacity of EE to promote granule cell production and cognitive memory was impaired in T1KO mice. Altogether, these findings indicate that CSPG underlies adult hippocampal neurogenesis and suggest that increased synthesis of CSPG may mediate promotion of granule cell production in response to EE.

Cohesin acetylation: from antiestablishment to establishment.

In a recent issue of Molecular Cell, Rowland et al. (2009) report that acetylation of cohesin in S phase transiently counteracts an intrinsic "antiestablishment" activity and, thus, enables establishment of sister chromatid cohesion.

Functional roles of CSPG4/NG2 in chondrosarcoma.

CSPG4/NG2 is a multifunctional transmembrane protein with limited distribution in adult tissues including articular cartilage. The purpose of this study was to investigate the possible roles of CSPG4/NG2 in chondrosarcomas and to establish whether this molecule may have potential for targeted therapy. Stable knock-down of CSPG4/NG2 in the JJ012 chondrosarcoma cell line by shRNA resulted in decreased cell proliferation and migration as well as a decrease in gene expression of the MMP (matrix metalloproteinase) 3 protease and ADAMTS4 (aggrecanase). Chondrosarcoma cells in which CSPG4/NG2 was knocked down were more sensitive to doxorubicin than wild-type cells. The results indicate that CSPG4/NG2 has roles in regulating chondrosarcoma cell function in relation to growth, spread and resistance to chemotherapy and that anti-CSPG4/NG2 therapies may have potential in the treatment of surgically unresectable chondrosarcoma.

Entrapment via synaptic-like connections between NG2 proteoglycan+ cells and dystrophic axons in the lesion plays a role in regeneration failure after spinal cord injury.

NG2 is purportedly one of the most growth-inhibitory chondroitin sulfate proteoglycans (CSPGs) produced after spinal cord injury. Nonetheless, once the severed axon tips dieback from the lesion core into the penumbra they closely associate with NG2+ cells. We asked if proteoglycans play a role in this tight cell-cell interaction and whether overadhesion upon these cells might participate in regeneration failure in rodents. Studies using varying ratios of CSPGs and adhesion molecules along with chondroitinase ABC, as well as purified adult cord-derived NG2 glia, demonstrate that CSPGs are involved in entrapping neurons. Once dystrophic axons become stabilized upon NG2+ cells, they form synaptic-like connections both in vitro and in vivo. In NG2 knock-out mice, sensory axons in the dorsal columns dieback further than their control counterparts. When axons are double conditioned to enhance their growth potential, some traverse the lesion core and express reduced amounts of synaptic proteins. Our studies suggest that proteoglycan-mediated entrapment upon NG2+ cells is an additional obstacle to CNS axon regeneration.

Mammalian target of rapamycin's distinct roles and effectiveness in promoting compensatory axonal sprouting in the injured CNS.

Mammalian target of rapamycin (mTOR) functions as a master sensor of nutrients and energy, and controls protein translation and cell growth. Deletion of phosphatase and tensin homolog (PTEN) in adult CNS neurons promotes regeneration of injured axons in an mTOR-dependent manner. However, others have demonstrated mTOR-independent axon regeneration in different cell types, raising the question of how broadly mTOR regulates axonal regrowth across different systems. Here we define the role of mTOR in promoting collateral sprouting of spared axons, a key axonal remodeling mechanism by which functions are recovered after CNS injury. Using pharmacological inhibition, we demonstrate that mTOR is dispensable for the robust spontaneous sprouting of corticospinal tract axons seen after pyramidotomy in postnatal mice. In contrast, moderate spontaneous axonal sprouting and induced-sprouting seen under different conditions in young adult mice (i.e., PTEN deletion or degradation of chondroitin proteoglycans; CSPGs) are both reduced upon mTOR inhibition. In addition, to further determine the potency of mTOR in promoting sprouting responses, we coinactivate PTEN and CSPGs, and demonstrate that this combination leads to an additive increase in axonal sprouting compared with single treatments. Our findings reveal a developmental switch in mTOR dependency for inducing axonal sprouting, and indicate that PTEN deletion in adult neurons neither recapitulates the regrowth program of postnatal animals, nor is sufficient to completely overcome an inhibitory environment. Accordingly, exploiting mTOR levels by targeting PTEN combined with CSPG degradation represents a promising strategy to promote extensive axonal plasticity in adult mammals.

Infarct-derived chondroitin sulfate proteoglycans prevent sympathetic reinnervation after cardiac ischemia-reperfusion injury.

Sympathetic nerves can regenerate after injury to reinnervate target tissues. Sympathetic regeneration is well documented after chronic cardiac ischemia, so we were surprised that the cardiac infarct remained denervated following ischemia-reperfusion (I-R). We used mice to ask if the lack of sympathetic regeneration into the scar was due to blockade by inhibitory extracellular matrix within the infarct. We found that chondroitin sulfate proteoglycans (CSPGs) were present in the infarct after I-R, but not after chronic ischemia, and that CSPGs caused inhibition of sympathetic axon outgrowth in vitro. Ventricle explants after I-R and chronic ischemia stimulated sympathetic axon outgrowth that was blocked by nerve growth factor antibodies. However, growth in I-R cocultures was asymmetrical, with axons growing toward the heart tissue consistently shorter than axons growing in other directions. Growth toward I-R explants was rescued by adding chondroitinase ABC to the cocultures, suggesting that I-R infarct-derived CSPGs prevented axon extension. Sympathetic ganglia lacking protein tyrosine phosphatase sigma (PTPRS) were not inhibited by CSPGs or I-R explants in vitro, suggesting PTPRS is the major CSPG receptor in sympathetic neurons. To test directly if infarct-derived CSPGs prevented cardiac reinnervation, we performed I-R in ptprs-/- and ptprs+/- mice. Cardiac infarcts in ptprs-/- mice were hyperinnervated, while infarcts in ptprs+/- littermates were denervated, confirming that CSPGs prevent sympathetic reinnervation of the cardiac scar after I-R. This is the first example of CSPGs preventing sympathetic reinnervation of an autonomic target following injury, and may have important consequences for cardiac function and arrhythmia susceptibility after myocardial infarction.

Eruptive and functional changes in periodontal ligament fibroblast orientation in CD44 wild-type vs. knockout mice.

BACKGROUND AND OBJECTIVE: Periodontal ligament (PDL) fibroblasts establish principal fibers of the ligament during tooth eruption, and maintain these fibers during occlusion. PDL development and occlusal adaptation includes changes in the orientation of PDL fibroblasts; however, the mechanism for these changes in orientation is unclear. The objective of this study was to compare PDL fibroblast orientation in different stages corresponding with first molar eruption and occlusion in CD44 wild-type (WT) and knockout (KO) mice. MATERIAL AND METHODS: CD44 WT and KO mice were raised to six postnatal stages corresponding with first molar (M1 ) eruption (postnatal day 8, 11, 14 and 18) and occlusion (postnatal day 26 and 41). Coronal sections of the first mandibular molar (M1 ) were prepared and the orientation of fibroblasts in the cervical root region was measured. Angle measurements were compared across developmental stages and between strains using Watson-Williams F-test (oriana software) and ANCOVA. RESULTS: PDL fibroblast orientation increased significantly in CD44 WT (9-87°) and KO mice (14-93°; p ≤ 0.05) between intraosseous eruption (day 11), mucosal penetration (day 14) and preocclusal eruption (day 18); however, the PDL fibroblast orientation did not change significantly with the onset of occlusion (day 26) or continued function (day 41). Within each strain, the variance in fibroblast orientation during preocclusal eruption (day 18) was significantly higher than the variance of all other time points (p < 0.0005). CD44 WT and KO mice showed a similar pattern of PDL development and eruption with a significant difference in CD44 WT vs. KO fibroblast orientations only during early function (day 26, 92° vs 116°; p = 0.05). CONCLUSIONS: The development of PDL fibroblast orientation is highly similar between CD44 WT and KO mice. Between early (day 11) and late (day 18) eruptive stages PDL fibroblast orientation increases, corresponding with the upward movement of M1 . The PDL fibroblast orientation established in preocclusal eruption (day 18) is maintained during early (day 26) and late (day 41) stages of occlusal function, suggesting that PDL cells adapt to mechanical loads in the oral cavity before M1 occlusion.

Intra-axonal translation of RhoA promotes axon growth inhibition by CSPG.

Chondroitin sulfate proteoglycans (CSPGs) are a major component of the glial scar that contributes to the limited regeneration of the CNS after axonal injury. However, the intracellular mechanisms that mediate the effects of CSPGs are not fully understood. Here we show that axonal growth inhibition mediated by CSPGs requires intra-axonal protein synthesis. Application of CSPGs to postnatal rat dorsal root ganglia axons results in an increase in the axonal levels of phosphorylated 4E-BP1, a marker of increased protein translation. Axons grown in media containing CSPGs exhibit markedly reduced growth rates, which can be restored by the selective application of protein synthesis inhibitors to distal axons. We show that these axons contain transcripts encoding RhoA, a regulator of the cytoskeleton that is commonly used by the signaling pathways activated by many inhibitors of axon growth. We also show that selective application of CSPGs to axons results in increased intra-axonal synthesis of RhoA and that depletion of RhoA transcripts from axons results in enhanced growth of axons in the presence of CSPGs. These data identify local translation as an effector pathway of CSPGs and demonstrate that local translation of RhoA contributes to the axon growth inhibitory effect of CSPGs.

Proteoglycans in the central nervous system: role in development, neural repair, and Alzheimer's disease.

Proteoglycans (PGs) are major components of the cell surface and extracellular matrix and play critical roles in development and maintenance of the central nervous system (CNS). PGs are a family of proteins, all of which contain a core protein to which glycosaminoglycan side chains are covalently attached. PGs possess diverse physiological roles, particularly in neural development, and are also implicated in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD). The main functions of PGs in the CNS are reviewed as are the roles of PGs in brain injury and in the development or treatment of AD.

[Inhibitory proteins of neuritic regeneration in the extracellular matrix: structure, molecular interactions and their functions. Mechanisms of extracellular balance]. / Proteinas inhibidoras de la regeneracion neuritica en la matriz extracelular: estructura, interacciones moleculares y sus funciones. Mecanismos del balance extracelular.

After injury of the central nervous system (CNS) in higher vertebrates, neurons neither grow nor reconnect with their targets because their axons or dendrites cannot regenerate within the injured site. In the CNS, the signal from the environment regulating neurite regeneration is not exclusively generated by one molecular group. This signal is generated by the interaction of various types of molecules such as extracellular matrix proteins, soluble factors and surface membrane molecules; all these elements interact with one another generating the matrix's biological state: the extracellular balance. Proteins in the balanced extracellular matrix, support and promote cellular physiological states, including neuritic regeneration. We have reviewed three types of proteins of the extracellular matrix possessing an inhibitory effect and that are determinant of neuritic regeneration failure in the CNS: chondroitin sulfate proteoglycans, keratan sulfate proteoglycans and tenascin. We also review some of the mechanisms involved in the balance of extracellular proteins such as isomerization, epimerization, sulfation and glycosylation as well as the assemblage of the extracellular matrix, the interaction between the matrix and soluble factors and its proteolytic degradation. In the final section, we have presented some examples of the matrix's role in development and in tumor propagation.

The versatile roles of lumican in eye diseases: A review.

Lumican is a keratan sulfate proteoglycan that belongs to the small leucine-rich proteoglycan family. Research has lifted the veil on the versatile roles of lumican in the pathogenesis of eye diseases. Lumican has pivotal roles in the maintenance of physiological tissue homogenesis and is often upregulated in pathological conditions, e.g., fibrosis, scar tissue formation in injured tissues, persistent inflammatory responses and immune anomaly, etc. Herein, we will review literature regarding the role of lumican in pathogenesis of inherited congenital and acquired eye diseases, e.g., cornea dystrophy, cataract, glaucoma and chorioretinal diseases, etc.

Targeted downregulation of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase significantly mitigates chondroitin sulfate proteoglycan-mediated inhibition.

Chondroitin sulfate-4,6 (CS-E) glycosaminoglycan (GAG) upregulation in astroglial scars is a major contributor to chondroitin sulfate proteoglycan (CSPG)-mediated inhibition [Gilbert et al. (2005) Mol Cell Neurosci 29:545­558]. However, the role of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S6ST) catalyzed sulfation of CS-E, and its contribution to CSPG-mediated inhibition of CNS regeneration remains to be fully elucidated. Here, we used in situ hybridization to show localized upregulation of GalNAc4S6ST mRNA after CNS injury. Using in vitro spot assays with immobilized CS-E, we demonstrate dose-dependent inhibition of rat embryonic day 18 (E18) cortical neurons. To determine whether selective downregulation of CS-E affected the overall inhibitory character of extracellular matrix produced by reactive astrocytes, single [against (chondroitin 4) sulfotransferase 11 (C4ST1) or GalNAc4S6ST mRNA] or double [against C4ST1 and GalNAc4S6ST mRNA] siRNA treatments were conducted and assayed using quantitative real-time polymerase chain reaction and high-performance liquid chromatography to confirm the specific downregulation of CS-4S GAG (CS-A) and CS-E. Spot and Bonhoeffer stripe assays using astrocyte-conditioned media from siRNA-treated rat astrocytes showed a significant decrease in inhibition of neuronal attachment and neurite extensions when compared with untreated and TGF-treated astrocytes. These findings reveal that selective attenuation of CS-E via siRNA targeting of GalNAc4S6ST significantly mitigates CSPG-mediated inhibition of neurons, potentially offering a novel intervention strategy for CNS injury.

Chondroitin sulfate proteoglycans regulate astrocyte-dependent synaptogenesis and modulate synaptic activity in primary embryonic hippocampal neurons.

It has been shown that astrocyte-derived extracellular matrix (ECM) is important for formation and maintenance of CNS synapses. In order to study the effects of glial-derived ECM on synaptogenesis, E18 rat hippocampal neurons and primary astrocytes were co-cultivated using a cell-insert system. Under these conditions, neurons differentiated under low density conditions (3500 cells/cm(2) ) in defined, serum-free medium and in the absence of direct, membrane-mediated neuron-astrocyte interactions. Astrocytes promoted the formation of structurally intact synapses, as documented by the co-localisation of bassoon- and ProSAP1/Shank2-positive puncta, markers of the pre- and postsynapse, respectively. The development of synapses was paralleled by the emergence of perineuronal net (PNN)-like structures that contained various ECM components such as hyaluronic acid, brevican and neurocan. In order to assess potential functions for synaptogenesis, the ECM was removed by treatment with hyaluronidase or chondroitinase ABC. Both enzymes significantly enhanced the number of synaptic puncta. Whole-cell voltage-clamp recordings of control and enzyme-treated hippocampal neurons revealed that chondroitinase ABC treatment led to a significant decrease in amplitude and a reduced charge of miniature excitatory postsynaptic currents, whereas inhibitory postsynaptic currents were not affected. When the response to the application of glutamate was measured, a reduced sensitivity could be detected and resulted in decreased currents in response to the excitatory neurotransmitter. These findings are consistent with the interpretation that the ECM partakes in the regulation of the density of glutamate receptors in subsynaptic sites.

Versican: a versatile extracellular matrix proteoglycan in cell biology.

Versican is a large extracellular matrix proteoglycan that is present in a variety of tissues. Successful cloning of the gene in man, mouse, cow and chicken has revealed the existence of at least four splice variants of versican, which differ in the size of the core protein and the number of glycosaminoglycan chains. The highly interactive nature of versican provides a basis for its importance as a structural molecule, creating loose and hydrated matrices during key events in development and disease; and by interacting either directly with cells or indirectly with molecules that associate with cells to, in part, regulate cell adhesion and survival, cell proliferation, cell migration and extracellular matrix assembly. Several studies within the past two years have confirmed a significant role for versican in regulating cell phenotype.

Identification of novel chondroitin proteoglycans in Caenorhabditis elegans: embryonic cell division depends on CPG-1 and CPG-2.

Vertebrates produce multiple chondroitin sulfate proteoglycans that play important roles in development and tissue mechanics. In the nematode Caenorhabditis elegans, the chondroitin chains lack sulfate but nevertheless play essential roles in embryonic development and vulval morphogenesis. However, assignment of these functions to specific proteoglycans has been limited by the lack of identified core proteins. We used a combination of biochemical purification, Western blotting, and mass spectrometry to identify nine C. elegans chondroitin proteoglycan core proteins, none of which have homologues in vertebrates or other invertebrates such as Drosophila melanogaster or Hydra vulgaris. CPG-1/CEJ-1 and CPG-2 are expressed during embryonic development and bind chitin, suggesting a structural role in the egg. RNA interference (RNAi) depletion of individual CPGs had no effect on embryonic viability, but simultaneous depletion of CPG-1/CEJ-1 and CPG-2 resulted in multinucleated single-cell embryos. This embryonic lethality phenocopies RNAi depletion of the SQV-5 chondroitin synthase, suggesting that chondroitin chains on these two proteoglycans are required for cytokinesis.

The human invariant chain is the core protein of the human class II-associated proteoglycan.

The human class II-associated chondroitin sulfate proteoglycan (CSPG) was analyzed biochemically and immunologically to determine a possible relationship with the human invariant chain (gamma 1) and its related components. The CSPG was purified by a three-step procedure involving associative ion-exchange chromatography, immunoprecipitation, and dissociative ion-exchange chromatography. Treatment of the CSPG with chondroitinase revealed core proteins of Mr approximately 46,000, 38,000, and 28,000, with the 38,000 species most highly represented. Tryptic peptide analysis revealed identity of the peptides of the 38,000 Mr core protein and gamma 1, and of the 28,000 Mr species and p25. The CSPG and its core proteins were shown to react directly with the mouse anti-human invariant chain monoclonal antibody VIC-Y1 and a rabbit antiserum produced against a synthetic peptide corresponding to the C-terminal end of invariant chain. These results demonstrate that the invariant chain is the core protein of the class II-associated CSPG. In addition, virtually all the CSPG was shown to be present on the cell surface.

Localized alteration of microtubule polymerization in response to guidance cues.

Inhibition of microtubule dynamic instability prevents growth cone turning in response to guidance cues, yet specific changes in microtubule polymerization as growth cones encounter boundaries have not been investigated. In this study, we examined the rate and direction of microtubule polymerization in response to soluble nerve growth factor (NGF) and immobilized chondroitin sulfate proteoglycans (CSPGs) by expressing enhanced GFP-EB3 in rat pheochromocytoma (PC12) cells. GFP-EB3 comets were monitored in live cells using time-lapse epifluorescent microscopy. With an automated tracking system, the rate of microtubule polymerization was calculated as the frame-to-frame displacement of EB3 comets. Our results demonstrate that the rate of microtubule polymerization is increased following NGF treatment, whereas contact with CSPGs decreases microtubule polymerization rates. This reduction in microtubule polymerization rates was specifically localized to neurites in direct contact with CSPGs and not at noncontacting neurites. Additionally, we found an increase in the percentage of microtubules polymerizing in the retrograde direction in neurites at CSPG boundaries, with a concomitant decrease in the rate of retrograde microtubule polymerization. These results implicate localized changes in microtubule dynamics as an important component of the growth cone response to guidance cues.

Collagen fibril organization in the pregnant endometrium of decorin-deficient mice.

In the pregnant mouse endometrium, collagen fibrillogenesis is characterized by the presence of very thick collagen fibrils which are topographically located exclusively within the decidualized stroma. This dynamic biological process is in part regulated by the small leucine-rich proteoglycans decorin and biglycan. In the present study we utilized wild-type (Dcn(+/+)) and decorin-deficient (Dcn(-/-)) time-pregnant mice to investigate the evolution of non-decidualized and decidualized collagen matrix in the uterine wall of these animals. Ultrastructural and morphometric analyses revealed that the organization of collagen fibrils in the pregnant endometrium of both non-decidualized and decidualized stroma showed a great variability of shape and size, regardless of the genotype. However, the decidualized endometrium from Dcn(-/-) mice contained fibrils with larger diameter and more irregular contours as compared to the wild-type littermates. In the Dcn(-/-) animals, the proportion of thin (10-50 nm) fibrils was also higher as compared to Dcn(+/+) animals. On day 7 of pregnancy, biglycan was similarly localized in the decidualized endometrium in both genotypes. Lumican immunostaining was intense both in decidualized and non-decidualized stroma from Dcn(-/-) animals. The present results support previous findings suggesting that decorin participates in uterine collagen fibrillogenesis. In addition, we suggest that the absence of decorin disturbs the process of lateral assembly of thin fibrils, resulting in very thick collagen fibrils with irregular profiles. Our data further suggest that decorin, biglycan and lumican might play an interactive role in collagen fibrillogenesis in the mouse endometrium, a process modulated according to the stage of pregnancy.

Impaired skin wound healing in lumican-null mice.

BACKGROUND: Previous studies have demonstrated that the lack of lumican delayed corneal wound healing in lumican-null (Lum(-/-) ) mice. This defect is rescued by the addition of glycosylated lumican core protein to the injured corneas. OBJECTIVES: We examined the hypothesis that lumican is also required for the healing of cutaneous wounds using Lum(-/-) mice. METHODS: We demonstrated the basic thinner skin phenotypes in Lum(-/-) mice at different time points and the changes in arrangement of collagen fibres by transmission electron microscopy (TEM). A full skin thickness wound was generated by punch biopsy (6 mm diameter) in experimental Lum(-/-) and wild-type mice. The closure of injured skin was measured after various periods of time (3, 6, 12, 18 days). Specimens of injured and uninjured skin (serving as control) were then subjected to morphological examination with haematoxylin and eosin and Masson trichrome stains, and by TEM. Immunohistochemical staining with anti-CD68 antibody was used to assess the presence of macrophages in injured skin healing for various periods of time. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to elucidate the transforming growth factor (TGF)-ß1-induced myofibroblast phenotypic genes. RESULTS: Skin of adult Lum(-/-) mice (3 months and older) was much thinner (40% less) than that of age-matched wild-type mice. This phenomenon was aggravated in older mice. TEM revealed disoriented and irregular collagen fibrils in the dermis of Lum(-/-) mice. Delayed wound healing with an increase in inflammatory macrophages was compatible with the delayed response of the expression of TGF-ß1, type I collagen α1 and fibronectin at the mRNA level by semiquantitative RT-PCR in the Lum(-/-) mice. CONCLUSIONS: Our data demonstrate that lumican plays pivotal roles in skin collagen fibrillogenesis and wound healing.